Panel structure having an intermediate filler of random oriented,resin rigidified particles of cellulosic material

ABSTRACT

THE DISCLOSURE INVOLVES A FORM OF PREFABRICATED STURCTURE SUCH AS COMMERCIAL OR INDUSTRIAL BUILDINGS, HOUSES OR ENCLOSURES EMPLOYING AN EXTERNAL SKIN BONDED TO AN INTERMEDIATE STRUCTURAL AND INSULATING FILLER WITH AN INNER SURFACE SKIN SIMILARLY BONDED TO THE FILLER MATERIAL. THE EXTERNAL SKINS ARE PREFERABLY RESIN BONDED GLASS FIBER AND THE INTERMEDIATE FILLER COMPOSES A RANDOM HONEYCOMB STRUCTURE MADE OF CELLULOSIC MATERIAL, SUCH AS INDIVIDUAL PIECES OR PAPER OF RANDOM SIZE EACH RIGIDIFIED AND BONDED TO ADJACENT PIECES BY A RESINOUS BINDER WHICH IS COMPATIBLE WITH THE BINDER OF THE SKINS. THE STRUCTURE IS SHOWN IN CONTINUOUS PANELS AND ACTUALLY THREE DIMENSIONAL STRUCTURE CONFIGURATIONS AS WELL AS DISCRETE STRUCTURAL ELEMENTS WHICH MAY BE USED TO REPLACE COMPARABLE STRUCTURAL ELEMENTS NORMALLY MADE OF WOOD. DISCLOSED ALSO ARE PROCESSES FOR CONTINUOUS MANUFACTURE OF STURCTURES EMPLOYING THE CONCEPT OF THIS INVENTION EITHER IN THE FACTORY OR ON SITE. THE SAME BASIC STRUCTURE IS SHOWN IN VARIOUS CONFIGURATIONS. ILLUSTRATED ARE A NUMBER OF PANEL SECTIONS EMPLOYING THE SAME STRUCTURE ARRANGEMENT BUT DIFFERENT FILLER OO21ING DENSITY WHEREBY THE LOAD BEARING STRENGTH OF THE PANEL MAY BE CONTROLLED AND ITS INSULATING PROPERTIES VARIED AS WELL. STRUCTURAL STRENGTH CAN ALSO BE VARIED BY CHANGING THE DIMENSIONS AND CONCENTRATIONS OF RESIN/FIBERGLAS OF EITHER OR BOTH EXTERNAL SKIN SURFACES. DISCLOSED ALSO ARE INDIVIDUAL STRUCTURAL ELEMENTS PRODUCED FROM WASTE PAPER MATERIAL AND RESIN BONDED SKINS.

3,837,989 RANDOM.

NTERMEDIATE FILLER 0F Sept. 24, 1974 PANEL STRUCTURE HAVING AN IORIENTED. RES IN RIGIDIFIED PARTICLES OF 7 CELLULOSIC MATERIAL 6Sheets-Sheet 1 Original Filed March 1970 FIG. 7 r

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FIG; 'I B Sept. 24, 1974 w, MCCOY 3,837,989

PANEL STRUCTURE HAVING AN INTERMEDIATE FILLER oE-Rmmou 0RIENTED, RESINRIGIDIFIED PARTICLES OF I CELLULOSIC MATERIAL Original'Filed March 2,1970 a Sheets Shet 6 United States Patent ftice 3,837,989 Patented Sept.24, 1974 3,837,989 PANEL STRUCTURE HAVING AN INTERMEDIATE FILLER OFRANDOM ORIENTED, RESIN RIGIDI- FIED PARTICLES F CELLULOSIC MATERIALWallace W. McCoy, 1471 Valane Drive, Glendale, Calif. 91208 Originalapplication Mar. 2, 1970, Ser. No. 15,364, now Patent No. 3,664,07 6.Divided and this application Apr. 19, 1972, Ser. No. 245,547 Int. Cl.1832b 3/12, /07, 5/16; B31d 3/02; E04!) 5/00 US. Cl. 161-68 6 'ClairnsABSTRACT OF THE DISCLOSURE This disclosure involves a form ofprefabricated structure such as commercial or industrial buildings,houses or enclosures employing an external skin bonded to anintermediate structural and insulating filler with an inner surface skinsimilarly bonded to the filler material. Theexternal skins arepreferably resin bonded glass fiber and the intermediate filler composesa random honeycomb structure made of cellulosic material, such asindividual pieces of paper of random size each rigidified and bonded toadjacent pieces by a resinous binder which is compatible with the binderof the skins. The structure is shown in continuous panels and actuallythree dimensional structure configurations as well as discretestructural elements which may be used to replace comparable structuralelements normally made of wood. Disclosed also are processes forcontinuous manufacture of structures employing the concept of thisinvention either in the factory or on site.

The same basic structure is shown in various configurations. Illustratedare a number of panel sections employing the same structure arrangementbut different filler density whereby the load bearing strength of thepanel may be controlled and its insulating properties varied as well.Structural strength can also be varied by changing the dimensions andconcentrations of resin/Fiberglas of either or both external skinsurfaces. Disclosed also are individual structural elements producedfrom waste paper material and resin bonded skins.

This is a division of application Ser. No. 15,364, filed Mar. 2, 1970,now Pat. 3,664,076.

BACKGROUND OF THE INVENTION Given a careful analysis, the constructionof houses has undergone only slight changes in the last one hundredyears. The most prevalent form of construction remains the balloonconstruction form of load bearing stud walls covered by exteriorsheathing and an interior facing. This mode of construction developedafter the Chicago fire has become the standard of the industry. In thefields of industrial and commercial construction, significant advanceshave been made using such techniques as curtain wall, panel and precastlift wall approaches. Even these techniques do not fully utilize theadvances which have been made in materials technology.

One example is in the area of resin bonded glass fibers, a materialcommonly used in automotive and marine fields but virtually unused inhousing structures. Another material advance which is just now reachingthe housing field is the use of ferro-concrete structures. This materialand form of construction, however, is incompatible with the need forthermal and sound insulation since it produces a thin to A in.) highlyconductive wall. In addition to the failure to use the new materialsavailable, housing construction is fast depleting our major naturalresource, our forests. Despite restoration, the drain is continuous andwith the current need to expand housmg, the rate W111 be accelerated.

The objects of this invention are all accomplished by the variousembodiments basically composed of a panel structure including two skinsurfaces, preferably of resin bonded glass fibers separated by anintermediate filler comprising random oriented resin rigidified particleof fragmented paper or other cellulosic material (interspaced) withintermediate random voids. The structure when viewed in section exhibitsthe general appearance of a random honeycomb. The intermediate fillermay be composed of cellulosic solid waste material that is currently abane of current urban existence and in this way is expected to reducethe drain on our forests.

BRIEF STATEMENT OF THE INVENTION I have determined that a major stepforward has been made in construction with the production in situ ofcontinuous panels employing and including outer skin, inner skininterconnecting insulation and structural core or fill to form acompleted structure of a shell in one continuous operation. Given thisbasic structure with a minimum of seams and a minimum of hand-carryingand holding by individuals that cost the time of construction can begreatly reduced. I have also determined that interior and exteriorsurface treatment or finish can be selected or produced during theconstruction of the structure. I have further determined it is possibleto produce a single structural form which can be made to provide therequired load bearing strength and insulation capability and the two canbe varied relatively independently to produce any combination desired.

I have also found the structure is made up by a pair of skin-likesurface members which are preferably resin bonded as indicated above andare in spaced parallel relationship. In between the two parallel skinsare a plurality of random oriented planar and non-planar pieces ofcellulosic material with a resinous binder. The cellulosic pieces arepreferably produced by random tearing of sheets of the material toproduce edge fibers and in certain embodiments, the individual piecesare ceased to provide a degree of inherent structural rigidity. Thepieces with their impregnating resin constitute relatively rigidinterconnecting members forming a random honeycomblike filler. Thesepieces are bonded to adjacent surface skins by the same or compatiblebonding agent as used for the filler.

DESCRIPTION OF THE DRAWINGS The foregoing features of this invention maybe more clearly understood from the following detailed description andby reference to the drawings in which:

FIG. 1 is a perspective view of a structural panel in accordance withthe invention with a portion of the outer skins cut away to expose thecore material.

FIG. 2 is an enlarged perspective view of the corner of the corematerial shown in FIG. 1.

FIG. 3 is a perspective view of a single particle of cellulose fiberbased material comprised of fragmented paper.

FIG. 4 is a perspective view of a single particle of fragmented paperafter deforming.

FIG. 5 is a cross sectional view of a corner of a complex panelstructure.

FIG. 6 is a perspective view of a structural beam havingintegrally-bonded skin surfaces.

FIG. 7 is a perspective view of a pipe having inner and outerintegrally-bonded skin surfaces.

FIG. 8 is a perspective view of a structural panel having reinforcingribs molded as a part of the lower skin surface.

FIG. 9 is a block diagram of the manufacturing process for the preferredcore material.

FIG. 10 is a cross sectional view of an extruder applyingintegrally-bonded skin surfaces to an uncured core preform to produce acomposite panel.

FIG. 10A is an alternate embodiment of a resin applicator forimpregnating the surface skins.

FIG. 10B is another alternate embodiment of a resin applicator forreinforcing and impregnating the surface skins.

FIG. 11 is a perspective view of an extruding machine producing ahollow, rectangular structural member.

FIG. 12 is a cross sectional view taken transversely across the machineillustrated in FIG. 11.

FIG. 13 is a perspective view of an extruding machine producing a hollowextrusion comprising the cross section of a gable-roofed buildingstructure.

FIG. 14 is a cross sectional view taken transversely across theextrusion illustrated in FIG. 13.

FIG. 15 is a perspective view of an extruding machine producing avertically-oriented panel along a fixed form.

FIG. 16 is a simplified perspective view of an extruding machineproducing a hollow tube having a flat bottom surface.

FIG. 17 is a simplified side elevation view of an extruding machineproducing a continuous pipe in a trench.

FIG. 18 is an enlarged perspective view of the end of a machine as inFIG. 17, producing a partially entrenched pipe.

Now refer to FIG. 1 wherein a perspective view of a structural panel 10is shown having a core 11 with generally coplanar surfaces 12 and 13,and edges 14 exposed. The core structure illustrated is comprised mainlyof loose cellulose-base fibrous material which has been impregnated witha plastic binder and compressed into the generally flat panel formshown. Surfaces 12 and 13 are relatively smooth in texture, havingassumed the approximate surface conditions of the integrally-bondedouter skins 15 and 16. Edges 14 are conversely somewhat rough andirregular, being illustrated as if the panel has been sawn from a largerpanel, and showing many edges and partial surfaces of particulatematerial and the interstices therebetween.

Now refer to FIG. 2 wherein an enlargement of the corner of the core 11in FIG. 1 is shown in sufificient magnification to more clearlyillustrate the structural make-up. A plurality of thin, irregularlyshaped and irregularly formed particles 20 are randomly oriented in alooselycompressed rigid form whereby their edges and surfaces providegenerally fiat and relatively smooth surfaces 12 and 13. The randomorientation of the particles 20 cause the resin-impregnated particles tointersect in irregular edge-to-edge, surface-to-surface, andedge-to-surface junctions whereby the total volume included issubstantially voids between the particles, and the rigidity of thestructure is developed by the stiffness of many open and closed cellsformed by the resin-stiffened complex-formed particles spanning betweenresin-bonded intersections. The cells appear as a random jumble ofinterlocked polyhedral shapes, very much like a form of honeycomb corewith the cell walls in complex form and scrambled in every possibledirection.

The core of the fragmentary cross section illustrated in FIG. 2nominally has a grayish cast and a rough texture on the edge similar tocoarse cork board. On closer examination, however, the rough texture isnot due to coarse, solid particles but to thin typically bent plateletsof material' clearly identifiable as fragments of newsprint, rigidifiedby resin.

Great amounts of voids are a dominate feature. The voids range widely insize and shape, with the maximum size on the order of an inch long andvarying widths, up to A of an inch. Loose platelets break when so bent.Throughout the exposed surfaces, many cellulose fibers, interlocking,adhering to flat surfaces of paper or just free are very obvious.

Experimental cores produced for tests, discussed later, when held in theair with one hand and struck soundly with the knuckles of the otherhand, give a damped ringing tone reminiscent of a wood plank, althoughif portion struck may also be accompanied by a small crushing sound, dueto the collapsing void in that immediate area.

The paper fragments visually range in size from roughly 2 inches down tothe limit of unaided vision. There appears to be a relatively evendistribution of size with an apparently large amount of free (at onetime) cellulose fibers.

The copius amount of voids are best seen in FIG. 2, along the edges. Itis difiicult in these illustrations to depict the wide ranging sizespresent, not the cellulosic fibers that are everywhere. A preferred sizeis /2 square inch.

Now refer to FIG. 3 wherein a typical particle of cellulose material 20is shown in a preferred embodiment employing waste newsprint paper asthe cellulose-base material. The particle 20 has a generally flatsurface 21, having small creases 24, bounded by very irregular edge 22generated by a tearing action, and is characterized by a ragged patternwith edge fibers 23 torn loose and extending from the torn edge.Experience has shown that more sharply cut particles do not have thecapability of retaining the impregnating resins at the particleintersections, whereas the torn edges promote better joint adhesion andimproved structural strength in the finished panel.

Now refer to FIG. 4 wherein a particle 20 is shown deformed considerablyout of its original planar form; and in which a plurality of creases orfolds 24 are provided in order to enhance the size and number of thevoids b..- tween the particles in the completed structural material, andto increase the column strength of the individual particles. Severalmethods are employed to produce and increase the folds in the particles.Initially, the tearing is done in a fragmentation process which strikesand tears the paper with considerable speed and violence, creating thesmaller creases 24 shown in FIG. 3. Then the resin impregnation isaccomplished in a mixing operation having an impeller action withsufficient vigor to further deform the particles. Subsequently, thecompression of the mass of material both in injecting the material intoa press and in compressing the panel to the desired thickness anddensity increases the folding by crumpling the precreased particles.Structural strength can also be varied by changing the dimensions andconcentrations of resin/ glass fibers of either or both external skinsurfaces.

Now refer again to FIG. 1 wherein skins 15 and 16 are shown definingplanar surfaces on each side of the panel 10. The composite structure isformed as the resin-impregnated skins 15 and 16 and the mass ofresin-impregnated loose, crumpled particles are simultaneously shapedand cured into an integral unit. The skins 15 and 16 may be completelyomitted from the panel for some specific structural applications wherethe surface texture and durability of the molded core faces 12 and 13 isadequate. Various resin concentrations will alter the appearanceconsiderably, as will the texture of the mold surface used. Many of thepanels fabricated as experimental models have exhibited pleasing colorand textures, and have a surface appearance very similar to dark-coloredcork board paneling.

The skins are preferably made of resin-bonded glass fibers. The glassfibers may be in the form of fabric, woven roving, chopped roving,random mat and prepregs of any of these. The glass fibers used generallyin experiments to date have been of the fabric variety, for ease ofhandling although chopped gun blown mat and random mat have been foundto be satisfactory. Normal glass fiber length for the blown random matwas 4 /2 inches. The glass fabric used for the bulk of the experimentalpanels was low cost, gray goods, 7 oz. triple strand fabric.

The resin system used in the skins is commercially available polyestertype with the following composition:

Resin System,

Dilution Monomer,

Inhibitor,

Activator, dimethyl phthalate, 0.6%,

Catalyst, methyl ethyl ketone peroxide, 1 /2%,

all percentages are by weight compared to the basic resinmonomer weight.

In some applications, it is desirable to have a panel which has a verydurable and weather resistant surface on one side, and a softer finishon the other side, as might be characterized by an outside wall of ahome or office. A suitable panel may be made by leaving the texture ofthe core exposed inside, and providing an integral outside skin of avery durable and weather resistant material, such as, laminatedFiberglas.

There are similarly many applications where it is imperative to havevery durable finishes on both surfaces, such as homes inhabited by smallchildren, schools, and other high traffic buildings. In these cases,suitable skins such as laminated resin bonded glass fibers polyvinylsheets, and even wood or simulated wood may easily be included at thetime of panel manufacture, and become permanent, integrally-bonded partsof the panel structure.

The natural of the manufacturing process wherein both the skins and thecore are formed and cured as an integral unit makes a much wider rangeof skin materials not only usable, but very practical from the viewpointof cost, strength, and appearance. Since the skin material before curingmay be nothing more than a resin-wetted, limp membrane, and the surfaceshape, texture and finish is replicated from the mold surface, then theskin material selection is extremely broad. For example, glass cloth,which is usually coarse, loosely-woven fabric, when saturated with resinand formed in a mirror-smooth mold will take on the mold finish andbecome a glossy, impervious, and easily maintained wall surface.Similarly, other textiles may be excellent choices for decorative wallsto produce very durable and attractive surfaces ranging from cottonprints through cheese-cloth to colored burlap, where the fabric isvisible, any texture is available from the mold surface, and the finalwall could resist even steam-cleaning if necessary.

There are less complex skin materials, such as papers, that are suitablefor integral panel formation, whereas they would not be practical tobond to a previously made core, such as in the processes used forhoneycomb panel manufacture. Compression-bonding of a geometrichoneycomb sandwich panel invariably leaves the pattern of the hexagonalcells on the surface of the paper faces, just as the longitudinalcorrugations are visible on corrugated paper board. Since in thisinvention the core particles are randomly distributed and partiallycrushed before curing, the flat surfaces of the core beneath the skinsare relatively smooth, planar and provide added structural and broadsupport areas for the skins. As a result, there is greatly reducedprint-through of the core texture, and there is never a regulargeometric pattern visible. As a result, the surface skins may beselected from thinner and lighter materials than is possible with ageometric patterned core.

The use of Kraft papers is very common in building materials, and iswell suited to use in the invention for applications having little or nomold texturing. In such the strength of the integral skins. Inapplications requiring huge puncture resistance, the need for heavyskins is obvious. In applications requiring resistance to heavy columnloading, it is necessary to provide higher strength and higher densityin the core materials. In applications requiring high bending strength,such as for unsupported spans, a stronger lower skin in tension iscombined with a fairly dense core to carry the compression loads.

Test panels were built up by hand using the following process. A moldwas made using an aluminum plate bottom surface which has a coating oflow adhesion material such as the tetrafluorethylene resin sold underthe trademark, Teflon, of the E. I. du Pont de Nemours & Inc. ofWilmington, Del. and sides of wood coated with the parting agent. Alayer of glass fabric, above described, is placed on the bottom plateand saturated with the same or compatible catalyzed resin. The requiredamount of the prepared core material is placed in the mold. (Therequired amount is determined by the desired compression ratio and thefinal thickness of the finished panel.) A sheet of glass fabricsaturated with resin is placed over the top of the core material and thewhole mass is compressed to the final desired thickness by weighting atopplate, which is of the same composition as the bottom plate. Theentire assemblage is allowed to polymerize in the mold. On completion ofthe polymerization process, the assemblage is removed from the mold andadditional layers of catalyzed resin are applied to the skin surfaces bybrush or squeegee, and allowed to polymerize. With the completion ofthis step, the test panels are finished.

A set of core samples were assembled to test the properties of the corematerial. The method of assembly was the same used for assembling thetest panels by hand described above, but without applying either skin tothe surfaces of the core. The appearance of the finished test cores weresimilar to the cores in the test panels.

Other material was used for potential core material. Dry straw, intendedfor feed use, was found very satisfactory. The length of the strawranged from 12 inches down to material that looked and behaved likepowder. There was also present 5 to 10% dirt and other ill-definedrefuse material. This seemed to have little negative effect on thestrength of the material.

Still another material tried was fresh grass clippings and dropped elmleaves. The presence of the water from the fresh green grass acted likean inhibiter to the polymerization process. It was necessary to bakethis sample for 12 hours at 180 F. before the core sample wasacceptable. The grass and leaves were used an natural, withoutfragmenting or masticating them. There was very little impregnation ofthe leaves or grass by the resin. This produced a core that hadunacceptable strength. If the material were dried and fragmented beforeassembly, then the core produced would be acceptable.

The ratio of resin to paper is on a weight basis. The final density isin pounds per cubic foot. The equivalent solid density is found bytaking the estimated solid density of the resin at 107 pounds per cubicfoot and the density of used newsprint at 36 pounds per cubic foot,applying the resin to paper ratio as a factor to determine what thedensity of the entire assemblage would be if there were no air voids init. The ratio between this value and the actual finish density is takenas the ratio of solid to void space in the core.

The newspaper used for the core contained a wide variety of paper types,including slick surface magazines. All of these paper types were foundusable except paper that was treated with chemicals that prevented theabsorption of the resin into the fibers of the paper. If the percentageof this type of paper was kept below 10% or if the paper was treated toincrease the absorbant properties, then this paper had littledeleterious effect.

Compression tests were made on the assembled panels.

The panels withstood compressive loads up to pounds per square inch withno signs of failure nor visible damage. The skins for this test panelwere 0.05 inches thick, containing one layer of 7 /2 oz. gray goodsglass fabric. The core used in the test panel had properties similar tocore sample four that will be described below.

The physical properties of the core material were determined from theskinless core samples described earlier. Various ratios of resin topaper were used as were different ratios of the compression of the corematerial. The results of this test sequence are summarized:

Compressive loading Ratio without resin to permanent paper by FinalPercent deformation, Core No. weight density void lb./in.

1. 94 5. 98 93 Not tested. 1. 40 9. 75 89 Do. 4. 37 11. 39 89. 2 45. 2.33 13. 30 86. 7 20. 1. 375 15. 87 88. 3 45. 5. 14 16. 01 85. 8 90. 2. 6317.00 84 Over 180 2.00 19. 90 80. 6 Do 1. 775 24. 2 Not tested 20.00 5.

Panels have been fabricated and tested for mechanical properties withoutany skins, with skins as minimal as lightweight cheesecloth, and withmuch heavier skins, including chopped glass fiber matting underlyingwoven glass fabric. Core samples have also been fabricated and testedusing varying densities of paper particles and resin concentrations. Insome experiments, natural materials were used in part or wholly as theparticles. These experiments were generally successful where a naturalorganic substitute closely approximated the configuration and absorptionof the paper particles. Where the natural substitute particles weregenerally fiat or at least thin and crinkled, and where they could bemasticated to increase crumpling and provide a loose pattern of edgefibers, the ideal particles were simulated closely enough to providestructural soundness. A number of samples made in densities of from 6 to20 pounds per cubic foot, having total void volumes of from 80% to 94%,and mechanical properties well suited to sawing, drilling, nailing, andthe like.

Now refer to FIG. wherein a more complex shape for a structure is shownin a typical corner cross section 25. The core material 14, as shown inFIG. 1, extends be tween the two skins 15 and 16 to form a rigidstructure. The complete structure having the corner shape isresinimpregnated, compressed and cured in a suitable mold providing thefinish and shape of the structure. All of the same parameters that arevariable for a simple panel are also variable in the more complexstructural members, the only significant difference being the shape ofthe mold used to produce the structure.

Now refer to FIG. 6 wherein a structural element 28 is shown having acore 14 and side skins 1S and 16, as shown in FIG. 1, and additionallyhaving edge skins 29 and 30 to complete the longitudinal enclosure ofthe core 14 to form a completely encased structural shape. Each of thefour skin finishes is produced by a mold surface which providestexturing and shape during curing of the resin-impregnated compositewhereby the result is an integrally-bonded structural member. A typicalexample of the end result is a 2 x 4 dimensional alike and directlyinterchangeable with wood structures of the same dimension.

Now refer to FIG. 7 wherein a pipe 31 is shown having a circular crosssection core 32, surrounded by an outer skin 33 and lined with an innerskin 34. The core material 32 is made up of the material described inFIG. 2, and both the inner and outer skin finishes are produced by moldsurfaces providing texturing and shape during curing of theresin-impregnated composite whereby the pipe is an integrally-bondedstructural member.

Now refer to FIG. 8 wherein a ribbed panel 38 having a core 39 made upof the material described in FIG. 2, an upper skin 40, and arib-contoured lower skin 41. Both of the skin finishes are produced bymold surfaces providing texturing and shape during curing of theresin-impregnated composite whereby the ribbed panel is anintegrally-bonded structural member. In the configuration shown in FIG.8, a unitary floor and support structure is produced. This continuouslower skin 41 forms the tension member of the assembly and the entirefloor acts as a unitary structural and surface assembly. The thicknessof the floor and skins, as well as filler-to-resin ratio, may be variedto produce a floor of the required strength and dimensionalcharacteristics. The complete bonding of the numerous particles to eachother and to the skin and the total absence of natural sheer planar inthe structure enhance its structural integrity.

In each of the foregoing embodiments, the same structural combination isused. One characteristic of this invention is that the same combinationmay be used to produce a lightweight non-self-supporting filler to astructural member. The panels may be varied in thickness, density andsize at will and in the production of continuous walls or panels, thethickness and density may even be varied as the structure is produced byvarying the mandrel separation and feed rate of material in the processdescribed below. In this manner, for example, the same structure may beused as interior non-load bearing and as exterior or load bearing wallswith only a change in the above parameters.

Now refer to FIG. 9 wherein a block diagram is shown for a preferredembodiment of the manufacturing process for the core material. Rawmaterial for the particles is shown as bulk paper 45, used newspapers46, and waste material 47. The selection of raw material depends on costand availability. Almost any cellulose fiber-based material is usable,and studies have shown even manmade trash to average 70% cellulose fibercontent. However, optimization of the mechanical properties of the corewill require control limits on raw material density, absorbtivity andtearing characteristics. Optimum skin thicknesses are 0.05 to 0.1 inch.

The raw materials, preferably used newspapers 46 which are available inlarge volume at very low cost, are fed into a fragmenter 50. Thefragmenter receives the paper into a. chamber where high speed rotatingfingers strike and tear the paper into at least lightly creasedirregular fragments. The fragmented material is conveyed to a mixed 51where rapidly rotating blades impact the fragment to further crease themand also mix in the resin 52 and catalyst 53. The resin is typically apolyester commercially available at low cost, including a resin systemof unsaturated polyester with maleic and phthalic anhydrides and atyrene dilution monomer, using hydroquinone stabilizer and a cobaltnaphthenate promoter. The catalyst is typically methyl ethyl ketoneperoxide.

The resin-impregnated particles are then conveyed to an extruder 54which partially compresses the mixture, thereby increasing the creasingof the particles somewhat, and extrudes the mixture into a continuousformer 55. The previously catalyzed resin-impregnated mass of particlesis further compressed into a desired shape by mechanical means by theformer 55 and is retained in the desired shape and becomes at leastpartially cured as the core material progresses through the former. Thepreferred embodiment of the manufacturing process for the core materialis shown as a continuous process wherein the output is a structuralmember 56 of undetermined length having limited width, thickness andshape established by the continuous former 55. An alternatemechanization is a batch process whereby measured amounts of materialsare processed in successive batches and the output is then a sequencedseries of individual pieces having all dimensions controlledsimultaneously.

The process for the manufacture of core material for integral curingwith one or more skins is substantially the same, except for onesignificant change in the operating mode of the former 55. When skinsare desired on the final structure, the former is adjusted to compressthe core to slightly less than the desired final thickness, and theoperating time and temperature are adjusted so the mixture does not curein the continuous former. The output of the process then is not a rigid,cured core structure 56, but instead is a slightly oversize uncuredpreform 57 suited for additional processing to complete the panelsstructure. Either output may be selected as an operating mode of thesame basic process and equipment.

Now refer to FIG. wherein a simplified extruder 58 is shown producing apanel having exterior skins. The output of the former 55 as in FIG. 9 isshown producing an uncured resin-impregnated preform 57. The preformmoves at a uniform rate synchronous with moving webs of skin membranematerial 60 and 61 supplied from rolls 62 and 63, respectively. Webs 60and 61 are impregnated with resin by applicators 64 and 65, and theresin is activated with catalyst by applicators 66 and 67. The webs 60and 61 and core preform 57 move together at a flared entrance formed bythe contour of the extrusion die wall 71 and 72. Temperature control asrequired by the panel thickness and resin characteristics is establishedby heater means 73 to promote curing, and by cooler means 74 to assistin removing exothermic heat from curing. The final taper of entrance 70and the spacin between die walls establish the thickness and crosssectional contour of the finished panel.

The movement of the panel materials through the extruder is produced bythree cooperating forces. First, the continuous former 55 supplies thepreform under pressure which tends to make the core flow through theextruder. Second, rollers 75 and provided with external power and engagethe cured walls of the finished panel 76 to pull the panel out of theextruding die walls 71 and 72. Third, a tension means 77 is provided tostart the process in operation when the die may not yet be filledsufficiently for normal operation. Friction of the work against the diewalls is controlled by the use of non-stick surfaces, such astetrafiuorethylene resin, as well as commercial parting agents. Thefriction is minimized in most applications where the die walls mustprovide texturing for the outer surfaces of the skins. In order toreplicate a complex threedimensional surface, however minute in depth,the die surface must move along with the skin surface. In an extrusionprocess, this necessarily implies a continuous surface, much like aconveyor belt 80 shown partially supported by rollers 81.

Now refer to FIG. 10A wherein a means for very uniform application ofcatalyzed resin is shown as an embodiment of the combination ofapplicators 65 and 66 or the combination applicators 64 and 67. The webof skin mate rial 60 passes bet-ween a pair of pressure rollers 81 and81a. A resin reservoir 82 and a catalyst reservoir 83 supply resin andcatalyst to the surface of roll 81, which in turn transfers the mixtureto web 60 at the junction of the pressure rolls. Control of the flowrate of the resin mixture with respect to the velocity of the web willproduce a meniscus 84 in which a constant rolling and mixing of theresin mixture takes place, and permitting a uniform amount of themixture to be carried with the web between the pressure rolls.

Now refer to FIG. 10B wherein a means is shown for applying a skinmaterial substantially made of non-woven fiber material, such as choppedglass fibers. The web 60 may be a very flimsy membrane, such ascheesecloth of thin tissue paper. A mixture of resin and catalyst 85 issprayed from a mixing spray gun 86 incorporating cutting and impellingrolls 87 and 88 so driven as to draw glass space fiber roving betweenthe rolls and dispense cut fibers 91. The fibers 91 are spray coatedwith resin mixture 85 to become the resin-saturated matting 92 carriedby the moving web 60.

Now refer again to FIG. 10 illustrating the cross section of an extruder58 in the process of manufacturing a panel. Additional skins may beplaced orthogonally to those shown in the illustration by simplyduplicating the components shown at to the section plane illustrated.This arrangement then extrudes structures having all four sides boundedby integrally-made surface skins. By varying the relative widths of theorthogonally placed webs and die surfaces structures may be producedcontinuously ranging from thin, edge-sealed panels to large, rectangularor square beams for structural use as illustrated in FIG. 6. Beams soextruded may duplicate the sizes of dimensioned lumber, so that 2 x 4s,2 x 12s, or even 12 x 18s are available in unlimited length withoutgrain, shrinkage, knots or warpage. The ability to vary density and skinstrength at will offers the opportunity to match the structuralproperties of the beam closely to the loads expected.

Now refer to FIG. 11 showing a perspective view of a machine so arrangedto extrude a completely closed hollow structure 101. The completeextruding machine 100 is comprised substantially of four orthogonallydisposed extruders 58 as shown in FIG. 10. The extruding machine iscarried on a means of self-propulsion 102, visible in part as a trackedvehicle. A continuous former 55, as described in the block diagram ofFIG. 9 and shown in FIG. 10, supplies the core preform to the fourinterconnected extruders 58, 58a, 58b and 580. The outer webs 61, 61a,61b and 61c may be seen coming from supply rolls 63, 63a, 63b and 63c;the inner rolls and webs being hidden from view. Ideally, the webs 61,61a-c are of greater width than their corresponding side of the finishedstructure to allow for overlap of the corners and increased strength.The four extruded panels 76, 76a, 76b and 760 are shown emerging fromthe extruding machine as a rectangular tube 101 having closed,integrally-made corners similar to the corner section described andillustrated in FIG. 5. The panel drive rollers 75 are not shown in FIG.11, and the extrusion force is instead aided by tension members 77, 77a,77b and 77c mutually fastened to an anchor means 103, whereby the freeend of the tube 101 remains in a stationary position as theself-propulsion means 102 carries the machine along the surface. Thestructure 101 may be of sufficient size to constitute an entire room orenclosure.

Now refer to FIG. 12 wherein the transverse cross section taken throughextruding machine 100 shows the rectangular tube 101 being formed insideand outside by the compression and shaping action of outer extrusion diesurfaces 71, 71a, 71b and 710, and inner extrusion die surfaces 72, 72a,72b and 720.

Now refer to FIG. 13 showing a perspective View of a more complexextrusion machine so arranged as to extrude a multi-panel closed, hollowstructure 111 of gable roof building form and including panels used as afloor 112, side walls 113 and 113a, a ceiling 114, a truss 115 and roofsections 116 and 116a. All of the interconnecting panels areintegrally-bonded and formed by machine 110, similar in function tomachine 100 shown in FIGS. 11 and 12, but more complex in shape, andcomprised of interconnected extruders of the type shown in FIG. 10,arranged and sized to produce the gabled extrusion shape 111.

Now refer to FIG. 14 wherein a transverse cross section taken acrossshape 11 shows a number of outer die surfaces 71d through 71scooperating with a number of inner die surfaces 72a through 72s tocompress and shape the gabled extrusion.

Now refer to FIG. 15 showing a perspective view of a single panelextrusion machine 120 so arranged as to extrude a vertical panel 121.The extruder itself, similar to extruder 58 in FIG. 10, has only one diesurface 122 associated with the self-propelled machine, the other diewall 123 being a fixed form along which the machine 120 travels. Theself-propelling means 124 moves the extruding machine along a wallsimilar to a concrete form wall, extruding the panel along the wallwhich may be later removed to expose the other surface of the panel. Thefreedom of movement of the machine permits the spacing between die wall122 and the fixed form wall 123 to be varied in operation, therebyproviding a means of constructing wall panels of continuously varyingstrength, weight and insulation values.

Now refer to FIG. 16 wherein a very simplified representation of anextruding machine 130 is shown producing a pipe or tunnel structure 131including a circular internal surface and a generally flat exteriorbottom surface 132. This extruded form is well suited for abovegroundtransmission of materials due to the design versatility that can beproduced by the basic extrusion system. The inner skin of the tube maybe made very high in hoop stress capability to carry fluids underpressure. The core material is an excellent insulator to reduce thepossibilty of overheating or freezing the transmitted fluids, and theouter skin offers security from ultra-violet degradation as well asmalicious or accidental puncture of the inner, highly-stressed tube.

Now refer to FIG. 17 wherein a simplified representation of a pipelaying extrusion machine 150 is shown manufacturing a pipe 151 byextruding the pipe in unstressed straight form directly into a trench153. The advantages of this form of manufacture is in the ease oftransportation of dense bulk raw materials to the pipeline site, asopposed to the less efficient transportation of bulky factory-made pipelengths, and the total elimination of the need for welding or couplingsdictated by the length of a truck bed.

Now refer to FIG. 18 showing an enlarged view of the end of the extruderof the machine 150 as illustrated in FIG. 17, with the pipe only partlyentrenched. In the configuration shown in FIG. 18, the trench mayactually act as the lower-half mold for the insulating filler and onlyemploy an outer skin 152 on the upper half with a continuous inner liner153. This system result in some saving of material in non-pressureapplications where a minimum of cost is the predominant factor.

In all of the foregoing figures, the concept of this invention and itsvarious applications in modes of in-situ production have beenillustrated. The primary characteristic of the invention relates to theuse of resin rigidifying discrete particles inter-laced with large voidareas, while used alone or in combination with protective surface skinsbound to the rigidified particles. One specific resin system isdisclosed in the application. It is recognized that other systems inaccordance with well-known practice in the plastics art might be used.Similarly, two compatible systems may be used-one for the filler andanother for the skin. The selection of the particular resin particleswill be dictated primarily on the basis of the application for the finalstructure and the economics, since the resin typically constitutes themajor cost of the structure.

Employing the in situ production of continuous structures, the laborcost of production has been minimized. These steps of handling,transportation, and erection of the structures have been virtuallyeliminated.

The above-described embodiments of this invention are merely descriptiveof its principles and are not to be considered limiting. The scope ofthis invention instead shall be determined from the scope of thefollowing claims including their equivalents.

What I claim is:

1. A structural material comprising substantially resinrigidizedparticles of at least cellulosic content in three dimensional randomorientations of particles intersecting in irregular edge to edge,surface to surface and edge to surface junctions with edge fibers ofadjacent particles in bonded engagement constituting a mass of rigidmaterial enclosing void regions of between and 94% of the volume of themass; said material having a density of 6-20 pounds per cubic foot and acompressive strength without permanent deformation of at least 20 poundsper square inch.

2. A structural panel comprising at least one relatively imperviousfacing of polymeric resin bonded material bonded to a filler of resinrigidified and bonded cellulosic particles of at least 70% cellulosiccontents of random size and orientation interspersed with voids ofbetween 80 and 94% by volume of said filler, said particles having edgefibers in resin bonded engagement with adjacent particles and defininginternal random honeycomb of compressive strength of at least 20 poundsper square inch.

3. The combination in accordance with Claim 2 comprising a panelincluding a pair of such impervious facings and in which the resinbonded filler comprises individual particles of paper having the centralportions of said particles of paper rigidified with resin and randomlyoriented to produce void regions constituting rigidified columnstructures and the edge regions having discrete fibers in resin bondedengagement with adjacent surfaces of said filler and said facingsthereby constituting a double sided panel having rigid random honeycombload transmitting filler therebetween.

4. The combination in accordance with Claim 3 wherein said particles ofpaper include fragmented edges in random interlocking relationship andresin bonded to adjacent particles.

5. The combination in accordance with Claim 3 wherein a number of theparticles of paper are in partially crushed condition defining localizedcolumn portions and the intermediate regions are rigidified with resinwhereby such particles constitute walls of a random honeycombassemblage.

6. The combination in accordance with Claim 2 wherein said fillerconstitutes resin bonded cellulose particles having a ratio of resin tocellulose by weight of 1.3 or greater.

References Cited UNITED STATES PATENTS 1,888,841 11/1932 Wenzel 52-4041,923,195 8/1933 Finck 52-404 2,175,630 10/1939 Kiesel 52-404 2,725,27111/1955 Cunningham 52-309 2,849,758 9/1958 Plumley 52-309 3,249,6595/1966 Voelker 26447 3,295,279 l/1967 Wilkins 52-268 3,630,813 12/1971Allen 161-43 3,647,606 3/1972 Notaro 161-52 PHILIP DIER, PrimaryExaminer US. Cl. X.R.

